IPv6, the successor standard to IPv4, for existing networks that currently use IPv4 communications could solve the basic problem of the availability of only approximately 4.3 billion IPv4 addresses. Ceasing use of IPv4 addresses and only using IPv6 addresses, however, is impractical and thus maintaining an environment that enables mutual communication between IPv4 and IPv6 (dual stack environment) will be required for a certain period. Completing IPv6 support is therefore considered to require a large amount of both time and money.
IPv6 addresses the main problem of IPv4, that is, the exhaustion of addresses to connect computers or host in a packet-switched network. IPv6 has a very large address space and consists of 128 bits as compared to 32 bits in IPv4. Therefore, it is now possible to support 2^128 unique IP addresses, a substantial increase in number of computers that can be addressed with the help of IPv6 addressing scheme. It is widely expected that the Internet will use IPv4 alongside IPv6 for the foreseeable future. IPv4-only and IPv6-only nodes cannot communicate directly, and need assistance from an intermediary gateway or must use other transition mechanisms.